IN vitro derived (IVD) sperm is just the latest development in stem cell research which has been commanding such media and public attention in recent years and is at the forefront of medical research.

While I sympathise with couples who are unable to have children, and would be the last person to refuse available medical treatment for myself and my family, I can’t help feeling that our continuing ability to increase the birth rate and extend life expectancy is the main cause of the world’s economic and social problems.

Unless the size of the population is allowed to reduce, there will be a bleak future for our children and grandchildren.

John Heslop, Durham City.